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BMA 125
Schematic
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BOSE BMA 125 Schematic

Table of Contents
SAFETY INFORMATION ................................................................................................................... 2
Electrostatic Discharge Sensitive (ESDS) ..................................................................................... 3
120V Version Specifications ........................................................................................................ 4-5
230V Version Specifications ........................................................................................................... 6
120V Disassembly/Assembly Procedures .................................................................................. 7-9
230V Disassembly/Assembly Procedures ..............................................................................10-12
BMA-125 Test Procedures 120V .............................................................................................. 13-16
BMA 125 Test Procedures 230V....................................................................................................16
Part List Notes................................................................................................................................ 17
Figure 1. 120V Chassis Layout...................................................................................................... 19
120V Amp PCB Part List ........................................................................................................... 20-22
120V Tone/Volume Control PCB Part List............................................................................... 23-24
120V Equalizer PCB Part List................................................................................................... 25-26
230V Main Assembly Part list .................................................................................................. 27-28
230V Amp PCB Part List ........................................................................................................... 29-31
230V Tone/Volume/Equalizer PCB Part List............................................................................32-35
Input Module 2B50 Part List..................................................................................................... 37-38
Figure 2. 2B37 Schematic and PCB Layout................................................................................... 39
Figure 3. 2B50 Schematic and PCB Layout................................................................................... 40
Figure 4. 120V Driver PCB Layout................................................................................................. 41
Figure 5. 120V Tone/Volume Control PCB Layout ......................................................................... 41
Figure 6. 120V Equalizer PCB Layout (Solder Side) ..................................................................... 42
Figure 7. 120V Equalizer PCB Layout (Component Side) ............................................................. 42
Figure 8. 230V Driver PCB Layout................................................................................................. 43
Figure 9. 230V Tone/Volume/Equalizer PCB Layout .................................................................... 44
Figure 10. and 11. 230V wiring diagram ...................................................................................45-46
1
SAFETY INFORMATION
1. Parts that have special safety characteristics are identified by the symbol on schematics or by special notes on the parts list. Use only replacement parts that
have critical characteristics recommended by the manufacturer.
2. Make leakage current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit before returning the unit to the customer. Use the following checks to perform these measurements:
A. Leakage Current Hot Check-With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. (Do not use an isolation transformer during this test.) Use a leakage current tester or a metering system that complies with American National Standards Institute (ANSI) C101.1 "Leakage Current for Appliances" and Underwriters Laboratories (UL) 1492 (71). With the unit AC switch first in the ON position and then in OFF position, measure from a known earth ground (metal water pipe, conduit, etc.) to all exposed metal parts of the unit (antennas, handle bracket, metal cabinet, screw heads, metallic overlays, control shafts, etc.), especially any exposed metal parts that offer an electrical return path to the chassis. Any current measured must not exceed 0.5 milliampere. Reverse the unit power cord plug in the outlet and repeat test. ANY MEASUREMENTS NOT WITHIN THE LIMITS SPECIFIED HEREIN INDICATE A POTENTIAL SHOCK HAZARD
THAT MUST BE ELIMINATED BEFORE RETURNING THE UNIT TO THE
CUSTOMER. B. Insulation Resistance Test Cold Check-(1) Unplug the power supply and
connect a jumper wire between the two prongs of the plug. (2)Turn on the power switch of the unit. (3) Measure the resistance with an ohmmeter between the jumpered AC plug and each exposed metallic cabinet part on the unit. When the exposed metallic part has a return path to the chassis, the reading should be between 1 and 5.2 Megohms. When there is no return path to the chassis, the reading must be "infinite". If it is not within the limits specified, there is the poss­ibility of a shock hazard, and the unit must be repaired and rechecked before it is returned to the customer.
2
Electrostatic Discharge Sensitive (ESDS)
Device Handling
This unit contains ESDS devices. We recommend the following precautions when repairing, replacing or transporting ESDS devices:
• Perform work at an electrically grounded work station.
• Wear wrist straps that connect to the station or heel straps that connect to conductive
floor mats.
• Avoid touching the leads or contacts of ESDS devices or PC boards even if properly grounded. Handle boards by the edges only.
• Transport or store ESDS devices in ESD protective bags, bins, or totes. Do not insert unprotected devices into materials such as plastic, polystyrene foam, clear plastic bags, bubble wrap or plastic trays.
CAUTION: THE FREESPACE® BUSINESS MUSIC AMPLIFIER
CONTAINS NO USER-SERVICEABLE PARTS. TO PREVENT WARRANTY INFRACTIONS, REFER SERVICING TO WARRANTY SERVICE STATIONS OR FACTORY SERVICE.
PROPRIETARY INFORMATION
THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF BOSE THE PURPOSE OF SERVICING THE IDENTIFIED BOSE PRODUCT
BY AN AUTHORIZED BOSE SERVICE CENTER OR OWNER OF THE BOSE PRODUCT, AND SHALL NOT BE REPRODUCED OR USED FOR ANY OTHER PURPOSE.
®
CORPORATION WHICH IS BEING FURNISHED ONLY FOR
3
120V VERSION SPECIFICATIONS
Power Output 125W Output Regulation Direct output: 0.5dB, no load to full load
Transformer outputs: 1.5dB, no load to full load
Input Sensitivity 2B37 dual input module
Input 1: Microphones: 1KΩ/350µV Auxiliary: 10KΩ/100mV Input 2: Microphones: 1KΩ/350µV Auxiliary: 10KΩ/1V Input 3 & 4: See instruction sheet enclosed with
module Input 5: 10KΩ/100mV Input 6: Mic Page: 150Ω/800µV
Nominal Load Voltage
Output Impedance 70.7V 40Ω (transformer)
25V 5Ω (transformer)
31.65V 8Ω (transformer)
22.35V 4Ω (direct)
Functional Outputs EQ Out: 1.0V into 600Ω (post-master volume)
Line Out: 1.0V into 600Ω (post-master volume) Tape Out: 650mV int o 10K Ω (pre-master volume) Mixer Output: 1.0V into 600Ω (pre-master volume)
Frequency Response at 9dB below rated output (EQ bypassed) EIA SE101A
Power Bandwidth at rated output/THD (EQ bypassed)
S/N Ratio All Controls left: 90dB
Tone Controls Bass: ±3dB at 85Hz
Direct: Transformer:
Direct: Transformer:
Input 5, Mic Page: 55dB Modules-Low Z Mic: 60dB Auxiliary: 70dB
Treble: ±3dB at 12.5KHz
20Hz - 20KHz, ±1dB
20Hz - 20KHz, +1dB/-2dB
20Hz - 20KHz, ±1dB (1% THD)
50Hz - 20KHz, +1dB/-2dB (1% THD)
4
120V VERSION SPECIFICATIONS
(Continued)
Mute >30dB (Mute Input 3, 4, 5) Control Interaction <1dB Power Outlet Unswitched AC Outlet 120VAC 60HZ, 500W AC Power
Consumption Temperature Range 12° F to 140° F (-10° C to + 60° C) Output Protection Electronic foldback and
thermal overload (both self-restoring) DC offset detection (for direct coupled output)
Size 17"W x 12.75"D x 4.5"H (43.2 X 32.4 x
Weight 27lb (12.3 Kg) Optional Modules 2B37 Dual input module Mic (screws)/Aux
2B50 Dual input module Mic (screws)/Stereo summing input (Aux) 2B42 Dual input module Aux/Telephone
120VAC, 60HZ at 3.0A at rated output (0.15A at idle)
11.4 cm) (desk mount) 19"W x 12.75"D x 5.25"H (48.2 x 32.4 x
13.3 cm) (rack mount)
5
230V VERSION SPECIFICATIONS
Power Output 125W Output Regulation Direct output: 0.5dB, no load to full load
Transformer outputs: 1.5dB, no load to full load
Input Sensitivity 2B37 dual input module
Input 1: Microphones: 200Ω/400mV Input 2: Auxiliary: 10KΩ/1V Input 3 & 4: See instruction sheet enclosed with module Input 5: 10KΩ/100mV Input 6: Mic Page: 150Ω/800µV
Output Impedance 100V 40Ω (transformer)
22.35V 4Ω (direct)
Functional Outputs EQ Out: 1.0V into 600Ω (post-master volume)
Line Out: 1.0V into 600Ω (post-master volume) Tape Out: 650mV into 10KΩ (pre-master volume) Mixer Output: 1.0V into 600Ω (pre-master volume)
Frequency Response at 9dB below rated output (EQ bypassed) EIA SE101A
Power Bandwidth at rated output/THD (EQ bypassed)
S/N Ratio All level Controls left: 90dB
Tone Controls Bass: ±3dB at 85Hz
Mute >30dB (Mute Input 3, 4, 5) Control Interaction <1dB AC Power Consumption 230VAC, 50HZ at 1.6A at rated output (0.7A at
Temperature Range 12° F to 140° F (-10° C to + 60° C) Output Protection Electronic foldback and
Direct: Transformer:
Direct: Transformer:
Input 5, Mic Page: 55dB Modules-Low Z Mic: 60dB Auxiliary: 70dB
Treble: ±3dB at 12.5KHz
thermal overload (both self­restoring) DC offset detection (for direct coupled output)
20Hz - 20KHz, ±1dB 20Hz - 20KHz, +1dB/-2dB
20Hz - 20KHz, ±1dB (1% THD) 50Hz - 20KHz, +1dB/-2dB (1% THD)
idle)
Size 17"W x 15"D x 5.75"H (43.2 X 38.1 x 14.6 cm)
(desk mount) 19"W x 15"D x 5.25"H (48.2 x 38.1 x 13.3 cm) (rack mount)
Weight 25lb (11.3 Kg)
6
120V DISASSEMBLY/ASSEMBLY PROCEDURES
1. Top Cover Removal
1.1 Remove the ten screws that secure the
top cover to the chassis. There are five on each side.
1.2 Lift the cover up.
2. Top Cover Replacement
2.1 Place the top cover over the chassis
and align the five screw holes on the top cover with the screw holes on the chassis.
2.2 Replace the ten screws that secure the top cover to the chassis. There are five screws on each side.
3. Input Module Removal
3.1 Remove the four screws that secure
the input module to the chassis.
5.3 Remove the three nuts that secure the input Five, bass and treble controls to the chassis.
5.4 Slide the PCB towards the rear of the unit until the potentiometer's shafts clear the holes in the chassis.
5.5 Lift the PCB up.
5.6 Remove the four screws that secure the
shield to the PCB.
5.7 Remove all wires attached to the PCB. Note: Make a note of the wiring configura-
tion before removing any wires.
6. Tone/Volume Control PCB Replace­ment
6.1 Attach the wires to the PCB.
3.2 Remove the input connector from the
input PCB.
3.3 Slide the input module out from the rear of the chassis.
4. Input Module Replacement
4.1 Slide the Input Module into the rear of
the chassis so that the labels are aligned with the labels on the chassis.
4.2 Replace the four screws that secure the input module to the chassis.
4.3 Connect the input connector to the input PCB.
5. Tone/Volume Control PCB Removal
5.1 Remove the two screws from the
bottom of the chassis that secure the PCB to the chassis.
5.2 Remove the input Five, bass and treble control knobs by pulling straight away on them.
6.2 Replace the four screws that secure the shield to the PCB.
6.3 Lower the PCB into the chassis and slide it forward until the shafts protrude out the front of the chassis.
6.4 Replace the three nuts that secure the input five, bass and treble control potenti­ometer to the chassis.
6.5 Replace the control shaft knobs by pushing them on.
6.6 Replace the two screws located on the bottom of the chassis that secure the PCB to the chassis.
7. Input 1, 2, 3, 4 and Master Volume Control Removal
7.1 Pull out on the knob to remove it.
7.2 Remove the nut that secures the pot's
shaft to the chassis.
7.3 Slide the pot out of the hole in the chassis.
7
120V DISASSEMBLY/ASSEMBLY PROCEDURES
7.4 Remove all the wires from the pot. Note: Make note of the wiring configura-
tion.
8. Input 1, 2, 3, 4 and Master Volume Control Replacement.
8.1 Attach the wires to the pot.
8.2 Insert the pot's shaft into the hole in
the chassis.
8.3 Replace the nut that secures the pot's shaft to the chassis.
8.4 Replace the control knobs by pushing them onto the pot's shaft.
9 Driver PCB Removal
9.1 Remove the four screws that secure
the Driver PCB to the chassis.
11.2 Remove the two screws that secure the equalizer to the chassis.
11.3 Lift the equalizer PCB up.
12. Equalizer PCB Replacement
12.1 Lower the equalizer PCB into the
chassis.
12.2 Replace the two screws that secure it to the chassis.
12.3 Connect the connector to the PCB.
13. Speaker Output Transformer Removal
13.1 Remove all the wires that connect the
transformer to the speaker output terminals and the driver PCB. Note: Make a note of the wiring configura­tion.
9.2 Remove all the connectors and wires from the PCB. Note: Make note of the wiring configura­tion.
9.3 Lift the Driver PCB up.
10. Driver PCB replacement
10.1 Lower the PCB into the chassis so
that the two large capacitors are located toward the transformer. Align the screw holes in the PCB with the standoffs on the chassis.
10.2 Replace the four screws that secure the driver PCB to the chassis.
10.3 Replace all the wires and connectors to the driver PCB.
11. Equalizer PCB Removal
11.1 Remove the connector from the
equalizer PCB.
13.2 Remove the four nuts that secure the transformer bracket to the chassis.
13.3 Remove the four screws and nuts that secure the transformer bracket to the transformer.
14. Speaker Output Transformer Replace­ment.
14.1 Replace the four screws and nuts that
secure the transformer bracket to the transformer.
14.2 Lower the transformer into the chas­sis and align the transformer so that the purple and brown wires face towards the rear of the chassis.
14.3 Replace the four screws that secure the transformer bracket to the chassis.
14.4 Replace the transformer's wires to the speaker output terminals and the driver PCB.
8
120V DISASSEMBLY/ASSEMBLY PROCEDURES
19. Output Transistor and Heat sink
15. Power Transformer Removal
Replacement.
15.1 Remove the wires that connect to the
AC outlet, power switch and driver PCB. Note: Make note of the wiring configura­tion.
15.2 Remove the four nuts that secure the transformer bracket to the chassis.
15.3 Remove the four screws and nuts that secure the transformer bracket to the transformer.
16. Power Transformer Replacement
16.1 Replace the four screws and nuts that
secure the transformer bracket to the transformer.
16.2 Lower the transformer into the chas­sis and align the transformer so that the wires face towards the inside of the unit.
19.1 Push the transistor into the transistor socket. Note: Inspect the mylar insulator for damage. Replace if necessary. Make sure the transistor and the transistor socket are flush with the heat sink.
19.2 Replace the two screws that secure the transistor to the heat sink.
19.3 Lower the heat sink into the chassis so that the screws holes in the heat sink align with the screw holes in the chassis.
19.4 Replace the four screws that secure the heat sink to the chassis.
16.3 Replace the four screws that secure the transformer bracket to the chassis.
16.4 Replace the wires that connect to the AC outlet, power switch and driver PCB.
17. Output Transistor and Heat sink Removal
18.1 Remove the four screws that secure
the heat sink to the chassis.
18.2 Lift the heat sink up.
18.3 Remove the two screws that secure
the transistor to the heat sink.
18.4 With a pair of pliers, grab onto the transistor and pull it out of the transistor socket.
9
230V DISASSEMBLY/ASSEMBLY PROCEDURES
1. Top Cover Removal
1.1 Remove the fourteen screws that
secure the top cover to the chassis. There are seven on each side.
1.2 Slide the top cover toward the rear of the unit and then lift it up.
2. Top Cover Replacement
2.1 Lower the top cover onto the chassis
and slide it toward the front of the unit.
2.2 Replace the fourteen screws that secure the top cover to the chassis. There are seven screws on each side.
3. Input Module Removal
3.1 Remove the four screws that secure
the input module to the chassis.
3.2 Remove the input connector from the input PCB.
5.3 Remove the two nuts that secure the PCB shield to the chassis.
5.4 Slide the PCB towards the rear of the unit until the potentiometer shafts clear the holes in the chassis.
5.5 Lift the PCB up.
5.6 Remove the four screws that secure
the shield to the PCB.
5.7 Remove the connectors from the PCB.
6. Tone/Volume/Equalizer PCB Replace­ment
6.1 Attach the connectors to the PCB.
6.2 Replace the four screws that secure
the shield to the PCB.
6.3 Lower the PCB into the chassis and slide it towards the front of the unit until the shafts protrude out the front of the chassis.
3.3 Slide the input module out from the rear of the chassis.
4. Input Module Replacement
4.1 Slide the input module into the rear of
the chassis so that the labels are aligned with the labels on the chassis.
4.2 Replace the four screws that secure the input module to the chassis.
4.3 Attach the input connector to the input PCB.
5. Tone/Volume/Equalizer PCB Removal
5.1 Remove the input five, bass and treble
control knobs by pulling them straight away from the unit.
5.2 Remove the three nuts that secure the input five, bass and treble controls to the chassis.
6.4 Replace the three nuts that secure the input five, bass and treble control pots to the chassis.
6.5 Replace the control shaft knobs by pushing them on.
6.6 Replace the two nuts that secure the PCB shield to the chassis.
7. Input 1, 2, 3, 4 and Master Volume Control Removal
7.1 Pull on the control knob to remove it.
7.2 Remove the nut that secures the pot's
shaft to the chassis.
7.3 Slide the pot out of the hole in the chassis.
7.4 Remove all wires from the pot. Note: Make note of the wiring configura-
tion.
10
230V DISASSEMBLY/ASSEMBLY PROCEDURES
8. Input 1, 2, 3, 4 and Master Volume Control Replacement
8.1 Attach the wires to the pot.
8.2 Insert the pot's shaft into the hole in
the chassis.
8.3 Replace the nut that secures the pot's shaft to the chassis.
8.4 Replace the control knobs by pushing them onto the pot's shaft.
9. Driver PCB Removal
9.1 Remove the seven screws that secure
the driver PCB to the chassis. One screw is located just below and between the two large capacitors.
9.2 Remove the connectors and the wires from the PCB. Note: Make note of the wiring configura­tion.
12. Speaker Output Transformer Replace­ment
12.1 Lower the transformer into the chas-
sis so that the wires face toward the rear of the unit.
12.2 Replace the four screws that secure the transformer to the chassis.
12.3 Attach the wires to the driver PCB and the speaker output terminals.
13. Power Transformer Removal
13.1 Remove the wires that connect to the
driver PCB, chassis terminal and the power switch.
13.2 Remove the four nuts that secure the transformer bracket to the chassis. Two of the nuts are located on the bottom of the chassis and two are located on the side of the chassis.
9.3 Lift the driver PCB up.
10. Driver PCB replacement
10.1 Lower the PCB into the chassis so
that the two large capacitors are located towards the front of the unit. Align the screw holes in the PCB to the holes in the chassis.
10.2 Replace the seven screws that secure the driver PCB to the chassis.
10.3 Replace the wires and connectors to the driver PCB.
11. Speaker Output Transformer Removal
11.1 Remove all the wires that connect the
transformer to the driver PCB and the speaker output terminals.
13.4 Lift the transformer up.
13.5 Remove the Four screws that secure
the transformer to the transformer bracket.
14. Power Transformer Replacement
14.1 Replace the four screws that secure
the transformer bracket to the transformer.
14.2 Lower the transformer into the chas­sis so that the black and blue wires face toward the driver PCB.
14.3 Replace the four nuts that secure the transformer bracket to the chassis.
14.4 Attach the wires to the driver PCB, chassis terminal and the power trans­former.
11.2 Remove the four screws that secure the transformer to the chassis.
11
230V DISASSEMBLY/ASSEMBLY PROCEDURES
15. Output Transistor and Heat Sink Removal
15.1 Remove the two nuts that secure the
heat sinks to the chassis.
15.2 Lift the heat sink up.
15.3 Remove the two screws that secure
the transistor to the heat sink.
15.4 With a pair of pliers, grab onto the transistor and pull it out of the transistor socket.
16. Output Transistor and Heat Sink Replacement
16.1 Push the transistor into the transistor
socket. Note: Inspect the mylar insulator for damage. Replace if necessary. Make sure the transistor and the transistor socket is flush with the heat sink.
16.2 Replace the two screws that secure the transistor to the heat sink.
16.3 Lower the heat sink into the chassis so that the screw holes in the heat sink align with the screws in the chassis.
16.4 Replace the two screws that secure the heat sink to the chassis.
17. Fuse replacement
17.1 Use a flat blade screw driver to pry off
the fuse holder located on the AC recep­tacle.
17.2 Pull the card out to expose the fuse. Lift the fuse out and replace it with a fuse of equal value. See the part list for the part number.
12
12
BMA-125 120V Test Procedures
2. 4
Ω Output
General Test Setup
Connect a 4Ω, 5Ω, 8Ω and 40Ω 200W load to the 4, 5, 8, and 40Ω outputs respectively.
Disconnect J1 (located at the equalizer PCB) and add a jumper from pin 1 (yellow) to pin 3 (violet) of the J1 connector. This will bypass the internal equalizer.
Set the tone controls to the center (flat) position unless otherwise noted.
1. Controls
1.1 Adjust Input Five to the full clockwise
position. Adjust the tone controls to their center (flat) position and all other volume controls to their full counter clockwise position.
1.2 Apply a 100mVrms, 1KHz signal to Input Five.
1.3 Using the Master volume control, adjust the output across the 4Ω load to 1Vrms. Reference a dB meter to the output.
1.4 Apply a 100mVrms, 85 Hz signal to Input Five. Rotate the bass control to the full counter clockwise position. Measure the output. It should be -3 dB
± 1dB.
Note: Remove the “4Ω” to “PRI” jumper. Connect a 4Ω load between “COM” and “4Ω”.
2.1 Apply a 105Vrms, 1KHz signal to Input Five. Adjust Input Five to full output at the 4Ω output (just before clipping).
2.2 Measure the voltage at the output. It should be
2.3 Measure the distortion. It should be < 0.5%.
2.4 With the 4Ω output adjusted to 24Vrms, reference a dB meter to the
output. Measure the response according to the following table.
Frequency Output
≥ 24Vrms.
(dB)
Tolerence
(dB)
20 Hz 0 -2 1 KHz ref -
20 KHz 0 -1.5
3. 8Ω Output
Note: Place a jumper between the output
connector labeled “4Ω” and the output connector labeled “PRI”. Connect an 8Ω load to the 8Ω output and the terminal marked lo.
1.5 Rotate the bass control to the full clockwise position. Measure the output. It should be 3 dB
1.6 Apply a 100mVrms, 10KHz signal to Input Five. Rotate the treble control to the full counter clockwise position. Measure the output. It should be -3.5 dB ± 1 dB.
1.7 Rotate the treble control to the full clockwise position. Measure the output. It should be 3.2 dB
± 1dB.
± 1 dB.
3.1 Apply a 120 mVrms, 1KHz signal to Input Five. Adjust Input Five to full output at the 8Ω output (just before clipping).
3.2 Measure the voltage at the 8Ω output. It should be
3.3 Measure the distortion. It should be < 0.5%.
3.4 With the 8Ω output adjusted to 31 Vrms, reference a dB meter to the
output. Measure the response according to the following table.
13
≥ 32Vrms.
BMA-125 120V Test Procedures
Frequency Output
(dB)
Tolerence
(dB)
50Hz 0 -2
1KHz ref -
20KHz 0 -2.8
3.5 Adjust Input Five until 11.2Vrms is measured across the 8Ω load. Reference a dB meter to the output.
3.6 Measure the response according to the following table.
Frque ncy Output
(dB)
Tolerence
(dB)
20Hz 0 -2
1KHz ref -
20KHz 0 -2.5
4. 25 Volt Output
4.5 Adjust Input Five until 8.875 Vrms is
measured across the 8Ω load. Reference a dB meter to the output.
4.6 Measure the response according to the following table.
Frequency Output
(dB)
Tolerence
(dB)
20Hz 0 -2
1KHz ref -
20KHz - -2.5
5. 70 Volt Output
Note: Place a jumper between the output
connector labeled “4Ω” and the output connector labeled “PRI”. Connect a 40Ω load to the 70V output and the terminal marked lo.
Note: Place a jumper between the output connector labeled “4Ω” and the output connector labeled “PRI”. Connect a 5Ω load to the 25V output and the terminal marked lo.
4.1 Apply a 120mVrms, 1KHz signal to Input Five. Adjust Input Five to full output at the 25V output (just before clipping).
4.2 Measure the output. It should be
≥ 25Vrms.
4.3 Measure the distortion. It should be < .5%.
4.4 With the 25V output adjusted to 25Vrms, reference a dB meter to the
output. Measure the response according to the following table.
Frequency Output
(dB)
Tolerence
(dB)
50Hz 0 -2 1KHz ref -
20KHz 0 -2.5
5.1 Apply a 105mVrms, 1KHz signal to Input Five. Adjust Input Five to full output at the 70 Volt output (just before clipping).
5.2 Measure the output. It should be
≥ 70.7 Vrms.
5.3 Measure the distortion. It should be < .5%.
5.4 With the output adjusted to 70.7Vrms,
reference a dB meter to the output. Mea­sure the response according to the follow­ing table.
Frequency Output
(dB)
Tolerence
(dB)
50Hz 0 -2 1KHz ref -
20KHz 0 -2.5
6. Tape Output
6.1 Apply a 100mV, 1KHz signal to Input
Five.
6.2 Adjust Input Five to the full clockwise position.
14
BMA-125 120V Test Procedures
6.3 Measure the Tape Output. It should be 1Vrms ( -.21, +.26).
7. Mixer Output
10.2 Reference a dB meter to the 4Ω
output.
10.3 Short the two screws labeled mute together.
7.1 Apply a 100mVrms, 1KHz signal to Input Five.
7.2 Adjust Input Five to the full clockwise position.
7.3 Measure the Mixer Output. It should be 1Vrms (-.2, +.29).
8. Line Output
8.1 Apply a 100mVrms, 1KHz signal to
Input Five.
8.2 Adjust Input Five to the full clockwise position.
8.3 Measure the line output. It should be .93Vrms (-.19, +.17).
9. Master Volume Control Range
9.1 Apply a 105mVrms, 1KHz signal to
Input Five. Adjust the Master volume control to the full clockwise position. Adjust Input Five to full output (just before clip­ping).
9.2 Reference a dB meter to the 4Ω output.
9.3 Rotate the Master volume control to the full counter clockwise position.
10.4 Measure the 4Ω output. It should be
≤ - 70dB.
11. Input 1 and 2: 400 Input
11.1 Apply a 400
Input 1 or 2. Move the selector switch to the Mic setting.
11.2 Reference a dB meter to the applied signal.
11.3 Measure the Line Output. It should be 67 dB
11.4 Reference a dB meter to the Line
Output.
11.5 Change the input signal to 20Hz. With the Mic EQ switch in the FLAT setting, measure the Line Output. It should be
-5.3 dB the LOCUT setting, it should be -24.8 dB
± 4 dB.
11.6 Change the input signal to 20KHz. With the Mic EQ switch in the FLAT setting, measure the Line Output. It should be
-1 dB the LOCUT setting, it should be -1 dB
± 1 dB.
± 2 dB. With the Mic EQ switch in
± 1 dB. With the Mic EQ switch in
µV Microphone
µVrms, 1KHz signal to
± 1 dB.
9.4 Measure the 4Ω output. It should be ≤ -50 dB.
10. Mute Control Attenuation
10.1 Apply a 105mVrms, 1KHz signal to
Input Five. Adjust the Master volume control to the full clockwise position. Adjust Input Five to full output (just before clip­ping).
11.7 Apply a 100mV, 1KHz signal to the INPUT 1 RCA jack or 1Vrms, 1KHz to INPUT 2.
11.8 Move the selector switch to the AUX setting. The LINE output should be clean.
Note: Perform the AUX test on both channels for the 220V variation.
15
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